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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 3 |
| 6 | 8 |
| 7 | 51 |
| 8 | 1329 |
| 9 | 393790 |
| 10 | 5670112879 |
| 11 | 43416847208976911 |
[0,0,0,0,1,3,8,51,1329,393790,5670112879, 43416847208976911] |